Suppose you have XML data that you want to regularly
send to Bob, across the Internet. But it is of a
confidential nature, so you don't want to send it as
plaintext. Well, you can try using low level
encryptions, like SSL or TLS. But these don't give any
authentication, ie. Bob can't tell that you actually
sent them. Also, once Bob gets the messages, they are
all in plaintext, so he can't easily protect these
against others, if he is on a multiuser computer.
One answer is to incorporate encryption into XML, by
defining cryptographic standards that sit atop XML,
and generate XML documents with encrypted data. These
let you and Bob use powerful XML-based routines like
XPath, XLink and XPointer. Plus, you can now do things
like append your digital signature to your plaintext
file, encrypt the combination with Bob's public key,
and get a resultant XML document that you can send
Bob. Upon receipt, he can decrypt it and verify that
you are the author, all the while dealing with XML
documents.
This book explains the emerging XML standards that
make this possible. They discuss at a high level the
various cryptographic algorithms, like AES [Advanced
Encryption Standard], Diffie-Hellman and MD5. Little
mathematics is needed, as they leave the mechanics of
the algorithms to other books. Instead, they describe
the XML infrastructure that uses these.
The book has a necessarily comprehensive description
of canonicalisation; which refers to the rewriting of
an XML document in a standard form, prior to
encryption. Otherwise two semantically identical
documents would give different ciphertexts, which is
confusing.
If you have been wondering if you should encrypt your
XML documents, and how to do so, this book may clarify
many issues.
